The progressive changes of neuronal activities of the nigral dopaminergic neurons upon withdrawal from continuous infusion of cocaine.

Sensitivity of the nigral dopamine neurons to intravenous apomorphine was examined in rats pretreated with continuous cocaine or saline for two weeks. One day after withdrawal from pretreatment, a subsensitivity was observed while a supersensitivity was found on day 7, along with a significant increase in the baseline firing rates. In humans, an increased sensitivity of dopamine soma/dendritic autoreceptors may partly account for the symptomatology associated with the intermediate phase of withdrawal from cocaine binges.